I have to agree with what all are saying but I cannot comment on what happened "In the good old days" as I am a newby to the sport having become involved only 5 years ago.
However I had been wanting to get into land sailing for a long time as I knew it was very fast. The only place I had ever seen it was on film. If you can recall the original "The Thomas Crown Affair" movie, I believe land sailing was one of the things Steve McQueen did when he was showing off his lifestyle to Faye Dunaway and my immediate reaction was "I want to do that!!!"
My introduction to the sport 5 years ago was via blokarts. As soon as my wife and I had a ride in one the love affair was instant and we were committed. A major factor in the decision to buy a couple of blokarts was their portability.
So as several people have said blokarts have done the sport a big favour by creating a resurgence through their portability and availability. As has also been said they do represent very good value for those that lack the skills or inclination for home building.
The number of clubs and frequency of organised events is a credit to blokart as well however I feel that scene is a tad "yuppyish" and exclusive. It is usually blokart or no kart, very controlled and the insurance ticket is the excuse to keep other yachts out. Maybe it's just me.

It wasn't long after owning a blokart that I started looking for something faster and less restrictive in design. For that reason I built "Diablo", a Lake Lefroy Mini Explorer. I hope also to build a class 5 soon.
Possibly the main thing slowing the spread of the sport is a generational thing. I think most or at least many of the people seen land yachting (including blokarting) tend to be of "baby boomer" vintage and the young people possibly then think that it is something for the oldies.
Even at blokart events it seems the younger ones involved are only there because their parents own the blokarts.
The financial barrier is a big consideration as unless one is skilled with tools it does need an investment of around $2,000 to get into the sport and that figure is based on second hand.
In the end though publicity has to be the key to gaining wider acceptance of and participation in the sport. There is public money available to better the sport via the federal and state government dept's of sport and recreation but the access to it is only via incorporated clubs. I have tried to get this across in the previous discussions about ALSA but nobody in ALSA seems interested. I don't want to start that arguement again but it is the same old question.
A democraticly representative body is needed to actively promote and market the sport to the general public. Cheers Cisco